Lithium manganese compound oxide and non-aqueous electrolyte secondary battery

ABSTRACT

The present invention provides a lithium manganese oxide, wherein a content of sulfur is not more than 0.32% by weight, and an averaged diameter of pores is not less than 120 nanometers, and the lithium manganese oxide is represented by Li 1+x Mn 2−x−y M y O 4 , where “M” is at least one of metals and 0.032≦x≦0.182; 0≦y≦0.2, and also provides a non-aqueous electrolyte secondary battery using the above lithium manganese compound oxide as a positive electrode active material.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a lithium manganese compoundoxide and a non-aqueous electrolyte secondary battery using the same asa positive electrode active material.

[0002] Non-aqueous electrolyte secondary batteries such as lithium ionsecondary batteries have been used as powers for mobile phones, notetype personal computers, cam coders as the non-aqueous electrolytesecondary batteries have small sizes and large capacities and are ofsealed type batteries.

[0003] The non-aqueous electrolyte secondary batteries are larger involume capacitance density or weight capacitance density and higher inoutput voltage than the aqueous electrolyte secondary battery. For thisreason, the non-aqueous electrolyte secondary batteries are highlyattractive for application not only to powers for small devices but alsoto powers for large devices.

[0004] The lithium ion secondary battery has a negative electrode madeof an active material such as carbon based material which islithium-doped or lithium-dedoped, and a positive electrode made of adifferent active material of compound oxide of lithium and transitionmetal. The negative electrode active material is applied on astripe-shaped negative electrode collector. The positive electrodeactive material is applied on a stripe-shaped positive electrodecollector. A separator is sandwiched between the positive and negativeseparators to form a laminated structure. This laminated stricture maybe coated with an armor material or be rolled to form a roll structure.The structure is contained in a battery can to form a battery.

[0005] As the positive electrode material for the lithium ion secondarybattery, lithium cobalt compound oxide or lithium manganese compoundoxide has been used. The secondary battery using the lithium manganesecompound oxide is larger in deterioration of the characteristics andperformances than the secondary battery using the lithium cobaltcompound oxide if the secondary batteries are subjected to thecharge/discharge cycle tests at a high temperature in the range of40-60° C.

[0006] A conventional technique for solving the above problem with thesecondary battery using the lithium manganese oxide as the positiveelectrode material is disclosed in Japanese laid-open patent publicationNo. 7-153496, wherein in order to prevent elution of manganese toelectrolyte, the lithium manganese compound oxide is added with at leastone oxide selected from BaO, MgO, and CaO for stabilization.

[0007] In Japanese laid-open patent publication No. 10-294099, it isdisclosed that the non-aqueous electrolyte secondary battery uses alithium manganese compound oxide which is prepared from a manganesecompound having both a sulfur content of not more than 0.6% by weightand a diffraction peak intensity in a specific range in an X-raydiffraction.

[0008] The lithium ion secondary battery using the lithium manganesecompound oxide such as lithium manganate as the positive electrodeactive material is engaged with the problem in deterioration in cycliccharacteristics and reduction in reservation capacity which may becaused by variation in properties of the positive electrode activematerial due to elution of manganese from lithium manganate and also bydeposition of eluted manganese on the negative electrode surface or heseparator surface as well as by deterioration of the electrolyte.

[0009] In the above circumstances, it had been required to develop anovel lithium manganese compound oxide and a novel non-aqueouselectrolyte secondary battery free from the above problem.

SUMMARY OF THE INVENTION

[0010] Accordingly, it is an object of the present invention to providea novel lithium manganese compound oxide free from the above problems.

[0011] It is a farther object of the present invention to provide anovel non-aqueous electrolyte secondary battery using a novel lithiummanganese compound oxide as a positive electrode active material,wherein the non-aqueous electrolyte secondary battery is free from theabove problems.

[0012] It is a still further object of the present invention to providea novel non-aqueous electrolyte secondary battery using a novel lithiummanganese compound oxide as a positive electrode active material,wherein the non-aqueous electrolyte secondary battery is superior incharge/discharge cyclic characteristics, preservation characteristicsand safety.

[0013] The present invention provides a lithium manganese oxide, whereina content of sulfur is not more than 0.32% by weight, and an averageddiameter of pores is not less than 120 nanometers, and the lithiummanganese oxide is represented by Li_(1+x)Mn_(2−x−y)M_(y)O₄, where “M”is at least one of metals and 0.0325≦x≦0.182; 0≦y≦0.2, and also providesa non-aqueous electrolyte secondary battery using the above lithiummanganese compound oxide as a positive electrode active material,

[0014] The above and other objects, features and advantages of thepresent invention will be apparent from the following descriptions.

DISCLOSURE OF THE INVENTION

[0015] The first present invention provides a lithium manganese oxide,wherein a content of sulfur is not more than 0.32% by weight, and anaveraged diameter of pores is not less than 120 nanometers, and thelithium manganese oxide is represented by Li_(1+x)Mn_(2−x−y)M_(y)O₄,where “M” is at least one of metals and 0.032≦x≦0.182; 0≦y≦0.2.

[0016] It is also preferable that the averaged diameter of pores is notless than 200 nanometers.

[0017] It is also preferable that the content of sulfur is not more than0.10% by weight.

[0018] It is also preferable that if the lithium manganese oxide isdried in at a temperature of 300° C. under an atmospheric pressure andsubsequently placed a temperature in the range of 20-24° C. and at arelative humidity in the range of 50-60% and for 48 hours, then amoisture content of the lithium manganese oxide is not more than 0.037%by weight.

[0019] The second present invention provides a lithium manganese oxide,wherein the lithium manganese oxide is represented byLi_(1+x)Mn_(2−x−y)M_(y)O₄, where “M” is at least one of metals and0.032≦x≦0.182; 0≦y≦0.2, and if the lithium manganese oxide is dried inat a temperature of 300° C. under an atmospheric pressure andsubsequently placed a temperature in the range of 20-24° C. and at arelative humidity in the range of 50-60% and for 48 hours, then amoisture content of the lithium manganese oxide is not more than 0.037%by weight.

[0020] It is also preferable that a content of sulfur is not more than0.32% by weight, and an averaged diameter of pores is not less than 120nanometers.

[0021] It is also preferable that the averaged diameter of pores is notless than 200 nanometers.

[0022] It is also preferable that the content of sulfur is not more than0.10% by weight.

[0023] The third present invention provides a positive electrode activematerial comprising a lithium manganese oxide, wherein a content ofsulfur is not more than 0.32% by weight, and an averaged diameter ofpores is not less than 120 nanometers, and the lithium manganese oxideis represented by Li_(1+x)Mn_(2−x−y)M_(y)O₄, where “M” is at least oneof metals and 0.032≦x≦0.182; 0≦y≦0.2.

[0024] It is also preferable that the averaged diameter of pores is notless than 200 nanometers.

[0025] It is also preferable that the content of sulfur is not more than0.10% by weight.

[0026] It is also preferable that if the lithium manganese oxide isdried in at a temperature of 300° C. under an atmospheric pressure andsubsequently placed a temperature in the range of 20-24° C. and at arelative humidity in the range of 50-60% and for 48 hours, then amoisture content of the lithium manganese oxide is not more than 0.037%by weight.

[0027] The fourth present invention provides a positive electrode activematerial comprising a lithium manganese oxide, wherein the lithiummanganese oxide is represented by Li_(1+x)Mn_(2−x−y)M_(y)O₄, where “M”is at least one of metals and 0.0329≦x≦0.182; 0≦y≦0.2, and if thelithium manganese oxide is dried in at a temperature of 300° C. under anatmospheric pressure and subsequently placed a temperature in the rangeof 20-24° C. and at a relative humidity in the range of 50-60% and for48 hours, then a moisture content of the lithium manganese oxide is notmore than 0.037% by weight.

[0028] It is also preferable that a content of sulfur is not more than0.32% by weight, and an averaged diameter of pores is not less than 120nanometers.

[0029] It is also preferable that the averaged diameter of pores is notless than 200 nanometers.

[0030] It is also preferable that the content of sulfur is not more than0.10% by weight.

[0031] The fifth present invention provides a non-aqueous electrolytesecondary battery having a positive electrode active material comprisinga lithium manganese oxide, wherein a content of sulfur is not more than0.32% by weight, and an averaged diameter of pores is not less than 120nanometers, and the lithium manganese oxide is represented byLi_(1+x)Mn_(2−x−y)M_(y)O₄, where “M” is at least one of metals and0.0325≦x≦0.182; 0≦y≦0.2.

[0032] It is also preferable that the averaged diameter of pores is notless than 200 nanometers.

[0033] It is also preferable that the content of sulfur is not more than0.10% by weight.

[0034] It is also preferable that if the lithium manganese oxide isdried in at a temperature of 300° C. under an atmospheric pressure andsubsequently placed a temperature in the range of 20-24° C. and at arelative humidity in the range of 50-60% and for 48 hours, then amoisture content of the lithium manganese oxide is not more than 0.037%by weight.

[0035] The sixth present invention provides a non-aqueous electrolytesecondary battery, wherein a positive electrode active materialcomprises a lithium manganese oxide represented byLi_(1+x)Mn_(2−x−y)M_(y)O₄, where “M” is at least one of metals and0.032≦x≦0.182; 0≦y≦0.2, and if the lithium manganese oxide is dried inat a temperature of 300° C. under an atmospheric pressure andsubsequently placed a temperature in the range of 20-24° C. and at arelative humidity in the range of 50-60% and for 48 hours, then amoisture content of the lithium manganese oxide is not more than 0.037%by weight.

[0036] It is also preferable that a content of sulfur is not more than0.32% by weight, and an averaged diameter of pores is not less than 120nanometers.

[0037] It is also preferable that the averaged diameter of pores is notless than 200 nanometers.

[0038] It is also preferable that the content of sulfur is not more than0.10% by weight.

[0039] The seventh present invention provides a method of forming alithium manganese oxide. The method comprises the steps of: mixing amanganese source and a lithium source to prepare a mixture; andsubjecting the mixture to a baking in an oxygen-containing atmosphere.

[0040] It is also preferable that the manganese source and the lithiumsource are mixed with each other at a ratio of lithium to manganese inthe range of 1.05 to 1.30.

[0041] It is also preferable that the mixture is baked at a temperaturein the range of 600-800° C. for 4-12 hours.

[0042] It is also preferable to further comprise the step of re-bakingthe mixture at a temperature in the range of 600-800° C. for 4-24 hours.

[0043] It is also preferable that the manganese source includes at leastone selected from the group consisting of electrolytic manganesedioxides, chemically synthesized manganese dioxides, manganese oxides,and manganese salts.

[0044] It is also preferable that the manganese source is prepared bythe steps of: subjecting the electrolytic manganese dioxide, Mn₂O₃, andMn₃O₄ to a heat treatment at a temperature in the range of 200-1000° C.in an oxygen-containing atmosphere.

[0045] It is also preferable that the manganese source is prepared bythe steps of subjecting the electrolytic manganese dioxide, Mn₂O₃, andMn₃O₄ to a cleaning with a water having a temperature in the range of20-40° C.; and carrying out a dry process in vacuum at a temperature of120° C.

[0046] It is also preferable that the manganese source is prepared bythe steps of: subjecting the electrolytic manganese dioxide, Mn₂O₃, andMn₃O₄ to a heat treatment at a temperature in the range of 200-1000° C.in an oxygen-containing atmosphere; carrying out a cleaning process witha water having a temperature in the range of 20-40° C.; and carrying outa dry process in vacuum.

[0047] It is also preferable that the manganese source is prepared bythe steps of: subjecting the electrolytic manganese dioxide, Mn₂O₃, andMn₃O₄ to a cleaning with a water having a temperature in the range of50-70° C.; and carrying out a dry process in vacuum at a temperature of120° C.

[0048] It is also preferable that the manganese source is prepared bythe steps of: subjecting the electrolytic manganese dioxide, Mn₂O₃, andMn₃O₄ to a heat treatment at a temperature in the range of 200-1000° C.in an oxygen-containing atmosphere; carrying out a cleaning with a waterhaving a temperature in the range of 50-70° C.; and carrying out a dryprocess in vacuum at a temperature of 120° C.

[0049] It is also preferable that the manganese source is prepared bythe steps of: subjecting the electrolytic manganese dioxide, Mn₂O₃, andMn₃O₄ to a cleaning with a diluted aqueous ammonia; and carrying out adry process in vacuum at a temperature of 120° C.

[0050] It is also preferable that the manganese source is prepared bythe steps of: subjecting the electrolytic manganese dioxide, Mn₂O₃, andMn₃O₄ to a heat treatment at a temperature in the range of 200-1000° C.in an oxygen-containing atmosphere; carrying out a cleaning with adiluted aqueous ammonia; and carrying out a dry process in vacuum at atemperature of 120° C.

[0051] The eighth present invention provides a method of forming alithium manganese oxide. The method comprises the steps of: subjectingan electrolytic manganese dioxide to a heat treatment at a temperaturein the range of 400-900° C. in an oxygen-containing atmosphere totransfer the electrolytic manganese dioxide to a manganese oxidecomprising one of β-MnO₂ and Mn₂O₃; subjecting the manganese dioxide toa water cleaning; and baking the manganese dioxide together with alithium compound.

[0052] It is also preferable that the manganese dioxide is bakedtogether with the lithium compound at a temperature in the range of750-900° C. in an oxygen-containing atmosphere.

[0053] It is also preferable to further comprise the step of: carryingout a re-baking process at a temperature in the range of 500-650° C. inan oxygen-containing atmosphere.

[0054] The above present inventions were made by having found the factsthat, in the battery having the positive electrode of the lithiummanganese compound oxide, deterioration in characteristics andperformances of the battery at high temperature is caused bydeterioration of the host structure of the manganese oxide due toelution of manganese component from the lithium manganese compound oxideand further by deposition of the eluted manganese component. The lithiummanganese compound oxide in accordance with the present invention has amodified spinel structure to solve the above problems with the lithiummanganese compound oxide having the normal spinel structure.

[0055] The improved lithium manganese compound oxide is characterized inthat the sulfur content is reduced and an averaged pore diameter ofmanganese spinel particles is enlarged.

[0056] The increase in he average pore diameter of the manganese spinelparticles reduces the content of a moisture adsorbed on the spinelparticles. An amount of the moisture to be adsorbed on the spinelparticles is reduced, even the spinel particles are exposed to an airhaving the moisture during the manufacturing process for forming thebattery. Further, the host structure of the manganese oxide isstabilized. Namely, both the reduction in the amount of the moistureadsorbed on the spinel particles and the stabilization of the hoststructure of the manganese oxide improve the characteristics andperformances of the battery.

[0057] As a result, the amount of the moisture introduced into thebattery is reduced to prevent the deterioration of the electrolyte ofthe battery.

[0058] The above improved lithium manganese compound oxide of thepresent invention is also characterized in that the residual amount ofsulfur is reduced. Sulfur present in the lithium manganese compoundoxide forms lithium sulfate, for which reason if the lithium manganesecompound oxide having a large residual sulfur contact is applied to thelithium ion battery, then the residual sulfur traps lithium ions.Accordingly, the reduction in the sulfur content of the lithiummanganese compound oxide reduces the number of the traps of the lithiumions, thereby allowing that the lithium ions diffused through the spinelstructure of the lithium manganese compound oxide are effectivelyutilized for reaction in the battery.

[0059] The lithium manganese compound oxide used as the positiveelectrode material for the non-aqueous electrolyte secondary battery maybe prepared by mixing a lithium source and a manganese source andsubsequently burning the mixture. It is preferable for the lithiumsource that compounds other than the lithium oxide, which are generatedby burning an oxide, a nitride or a hydroxide, may be dispersed in agaseous state, whereby the lithium oxide only remains.

[0060] It is possible to use, as the manganese source, manganesecompounds such as electrolytic manganese dioxides, chemicallysynthesized manganese dioxide, various manganese oxides, for example,Mn₂O₃ and Mn₃O₄, and manganese salts, for example, MnCO₃ and Mn(OH)₂. Itis preferable that the electrolytic manganese dioxide is subjected toammonia for neutralization to acid. It is particularly preferable thatthe content of the sulfur group is low.

[0061] It is also preferable that the manganese source is prepared bythe steps of: subjecting the electrolytic manganese dioxide, Mn₂O₃, andMn₃O₄ to a heat treatment at a temperature in the range of 200-1000° C.in an oxygen-containing atmosphere.

[0062] It is also preferable that the manganese source is prepared bythe steps of subjecting the electrolytic manganese dioxide, Mn₂O₃, andMn₃O₄ to a cleaning with a water having a temperature in the range of20-40° C.; and carrying out a dry process in vacuum at a temperature of120° C.

[0063] It is also preferable that the manganese source is prepared bythe steps of subjecting the electrolytic manganese dioxide, Mn₂O₃, andMn₃O₄ to a heat treatment at a temperature in the range of 200-1000° C.in an oxygen-containing atmosphere; carrying out a cleaning process witha water having a temperature in the range of 20-40° C.; and carrying outa dry process in vacuum.

[0064] It is also preferable that the manganese source is prepared bythe steps of subjecting the electrolytic manganese dioxide, Mn₂O₃, andMn₃O₄ to a cleaning with a water having a temperature in the range of50-70° C.; and carrying out a dry process in vacuum at a temperature of120° C.

[0065] It is also preferable that the manganese source is prepared bythe steps of: subjecting the electrolytic manganese dioxide, Mn₂O₃, andMn₃O₄ to a heat treatment at a temperature in the range of 200-1000° C.in an oxygen-containing atmosphere; carrying out a cleaning with a waterhaving a temperature in the range of 50-70° C.; and carrying out a dryprocess in vacuum at a temperature of 120° C.

[0066] It is also preferable that the manganese source is prepared bythe steps of: subjecting the electrolytic manganese dioxide, Mn₂O₃, andMn₃O₄ to a cleaning with a diluted aqueous ammonia; and carrying out adry process in vacuum at a temperature of 120° C.

[0067] It is also preferable that the manganese source is prepared bythe steps of: subjecting the electrolytic manganese dioxide, Mn₂O₃, andMn₃O₄ to a heat treatment at a temperature in the range of 200-1000° C.in an oxygen-containing atmosphere; carrying out a cleaning with adiluted aqueous ammonia; and carrying out a dry process in vacuum at atemperature of 120° C.

[0068] Lithium carbonate is preferable as the lithium source for thelithium manganese compound oxide.

[0069] Preferably, in the previous steps to the mixing step for mixingthe lithium source and the manganese source, the lithium source materialsuch as lithium carbonate is grounded, and the manganese source such asthe electrolytic manganese dioxide is classified, thereby to improve thereactivity and to obtain the lithium manganate with desired particlediameters.

[0070] In the mixing step for mixing the lithium source and themanganese source, it is preferable that the manganese source and thelithium source are mixed with each other at a ratio of lithium tomanganese in the range of 1.05 to 130, and the obtained lithiummanganese compound oxide has the compositional ratio represented byLi_(1+x)Mn_(2−x−y)M_(y)O₄, where “M” is at least one of metals and0.032≦x≦0.182; 0≦y≦0.2, and preferably Li_(1+x)Mn_(2−x)O₄, where0.032≦x≦0.182.

[0071] It is also preferable that the mixture of the manganese compoundand the lithium compound is baked at a temperature in the range of600-800° C. for 4-12 hours and in the oxygen-containing atmosphere andsubsequently the mixture is re-backed in the oxygen-containingatmosphere at a lower temperature in the range of 600-800° C. for 4-24hours.

[0072] It is particularly preferable that the electrolytic manganesedioxide as the source material is subjected to a heat treatment in anoxygen-containing atmosphere to transfer the electrolytic manganesedioxide to a manganese oxide comprising β-MnO₂ or Mn₂O₃ before themanganese dioxide is then subjected to a water cleaning or a warm watercleaning to obtain the manganese oxide, so that this manganese oxide ismixed with the lithium source for subsequent baking process at atemperature in the range of 750-900° C. in an oxygen-containingatmosphere and further a re-baking process at a temperature in the rangeof 500-650° C. in the oxygen-containing atmosphere to obtain the lithiummanganese oxide. Thereafter, this lithium manganese oxide is subjectedto a cleaning with an ordinarily water or a warm water and subsequentvacuum dry process at a temperature of 120° C.

[0073] The averaged pore diameter of the lithium manganese oxide ispreferably not less than 120 nanometers and more preferably not lessthan 200 nanometers, provided that the averaged pore diameter ismeasured by a mercury polosimeter method.

[0074] The sulfur content of the lithium manganese compound oxide ispreferably not more than 0.32% by weight and more preferably 0.10% byweight, provided that the sulfur content of the lithium manganesecompound oxide is measured in accordance with JIS K1467.

[0075] For the non-aqueous electrolyte secondary battery utilizing theimproved lithium manganese compound semiconductor as the positiveelectrode active material, the positive electrode may be formed asfollows. Powders of the improved lithium manganese compound oxide, anelectrically conductive material for providing an conductivity, a binderand a slurry with a dispersion medium solving the binder are applied ona collector such as an aluminum foil before drying process androll-compression process to form a film.

[0076] The conductive material for providing the conductivity may be amaterial having a large conductivity and being highly stable in thepositive electrode, for example, carbon black, natural black carbon,artificial carbon black and carbon fibers, The binder may preferably bea fluorine resin such as polytetrafluoroethylene and polyvinylidenefluoride. Particularly, polyvinylidene fluoride is preferably as beingsoluble with a solvent and easy to be mixed into the slurry.

[0077] The electrolyte to be used for the non-aqueous electrolytesecondary battery in accordance with the present invention is such thata supporting salt is solved into a non-aqueous solvent. The solvent maybe one of carbonates, chlorinated hydrocarbon, ethers, ketones, andnitriles. Preferably, the solvent comprises a mixture of at least oneselected from the first groups consisting of high dielectric solventssuch as ethylene carbonate, propylene carbonate, and gamma-butyrolactoneand of at least one selected from the second groups consisting of lowviscosity solvents such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, esters. Particularly, a mixture of ethylene carbonateand diethyl carbonate and a mixture of propylene carbonate and ethylmethyl carbonate are preferable.

[0078] The supporting salt may comprise at least one selected from thegroup consisting of LiClO₄, LiI, LiPF₆, LiAlCl₄, LiBF₄, and CF₃SO₃Li. Aconcentration of the supporting salt in the solvent is preferably in therange of 0.8-1.5 mol.

[0079] The non-aqueous solvent is generally hard to completely removemoisture therefrom, and is likely to adsorb the moisture in themanufacturing process for the battery. It is, therefore, likely that thesupporting salt reacts with this slight amount of moisture to generatehydrogen ions. However, the improved lithium manganese compound oxide ofthe present invention is capable of controlling the entry of themoisture into the battery, thereby preventing the deterioration of theelectrolyte of the battery.

[0080] The negative electrode active material may be one of lithium,lithium alloys, lithium-doped materials, lithium-dedoped materials,carbon materials such as graphites and amorphous carbon, and metalcompound oxides.

[0081] The separator may comprise one of a woven fabric, a non-wovenfabric, and a porous membrane. A polypropylene or polyethylene porousmembrane is preferable as being a thin film and having a large area, asufficient film strength and a desirable sheet resistance.

[0082] The non-aqueous electrolyte secondary battery may have such astructure that alternating laminations of positive and electrodesseparated by separators, or a roll of stripe-shaped alternatinglaminations of positive and electrodes separated by separators. Theexternal shape of the battery may be either a laminated shape, acylinder shape, a sheet shape, or a disk-shape or any other shape.

EXAMPLE

[0083] (Synthesis of Lithium Manganese Compound Oxide)

[0084] An electrolytic manganese dioxide was subjected to aneutralization with ammonia to prepare the neutralized electrolyticmanganese dioxide which has a sulfur group content of 1.1% by weight andan ammonium group content of 0.08% by weight. The electrolytic manganesedioxide was then subjected to heat treatments and cleaning processesunder various conditions to prepare various manganese source samples.

[0085] Lithium carbonate was grounded to have a center particle diameterD₅₀ of 1.4 micrometers, where D₂₅=1.0 micrometers, and D₇₅=1.8micrometers.

[0086] Subsequently, the lithium source and the manganese source weremixed with each other at a mole ratio of 2Li/Mn=1.10, and this mixturewas baked in an oxygen-aeration atmosphere at 800° C. for 12 hours. Thisbaked mixture was cooled and then re-baked at 650° C. for 12 hours. Fineparticles of diameters of not more than 1 micrometers were removed fromthe obtained particles by an air classifier to obtain various lithiummanganese oxides different in sulfur content and pore diameter from eachother.

[0087] (Preparation of Cylindrically Shaped Battery)

[0088] Subsequently, the various lithium manganese oxides different insulfur content and pore diameter from each other were used to preparevarious cylindrically shaped batteries through the following process.

[0089] Preparation of Positive Electrode: Lithium manganese oxide 90parts by weight Carbon black  6 parts by weight Polyvinylidene fluoride 4 parts by weight

[0090] 100 parts by weight of a mixture of the above materials wasdispersed into 61 parts by weight of N-methyl-2-porolidone to apply thesame onto an aluminum foil having a thickness of 20 micrometers toprepare a positive electrode.

[0091] Preparation of Negative Electrode: Carbon material (Osaka GasMCMB) 90 parts by weight Carbon black  2 parts by weight Polyvinylidenefluoride  8 parts by weight

[0092] 100 parts by weight of a mixture of the above materials wasdispersed into 117 parts by weight of N-methyl-2-porolidone to apply thesame onto a copper foil having a thickness of 15 micrometers to preparea negative electrode.

[0093] A porous polyethylene film having a thickness of 25 micrometerswas sandwiched between the above obtained positive and negativeelectrodes to form laminations. The laminations were rolled to form aroll structure. This roll structure was then contained in acylindrically shaped battery can for 18650-type battery, wherein thecylindrically shaped battery can has a diameter of 10 millimeters and aheight of 65 millimeters. A solvent was prepared, which has a volumeratio of ethylene carbonate diethyl carbonate=50:50 and solved with 1mol of LiPF₆ as a supporting salt. The solvent was injected into thebattery can as electrolyte and the battery can was sealed.

[0094] The batteries different in characteristics and properties of thelithium manganese compound oxides were measured in cyclic characteristicand reservation characteristic by the following evaluation methods andmeasured results are shown on the below table 1.

[0095] Samples having the cyclic characteristics of not less than 50%and the reservation characteristic of not less than 70% and having theaveraged pore diameter of not less than 120 nanometers were selected.The selected samples but different in sulfur content from each otherwere further measured in the cyclic characteristic and the reservationcharacteristic and measured results are shown on the below table 2.

[0096] From table 2, it can be understood that as the sulfur content islow, then both the cyclic characteristic and the reservationcharacteristic are improved. Preferable samples are that the cycliccharacteristic is not less than 60% and the reservation characteristicis 80% and the sulfur content is not more than 0.32% by weight.

[0097] Samples different in the re-adsorbed moisture content and theaveraged pore diameter from each other were measured in the cycliccharacteristic and the reservation characteristic and measured resultsare shown on the below table 3.

[0098] From table 3, it can be understood that as the re-adsorbed ismoisture content is low, then the battery characteristics andperformances are improved. The re-adsorbed moisture content tends to below as the averaged pore diameter is small. Preferable samples are suchthat the cyclic characteristic is not less than 50% and the reservationcharacteristic is 70% and the sulfur content is not more than 0.037% byweight.

[0099] Further, samples having the re-adsorbed moisture content of notmore than 0.037 were selected. The selected samples but different insulfur content from each other were measured in the cycliccharacteristic and the reservation characteristic and measured resultsare shown on the below table 4.

[0100] (Evaluation Method)

[0101] 1. Measurement to Pore Diameter

[0102] 0.5 g of the lithium manganese compound oxide was delaminated andthen placed into measuring cells of a pore diameter distributionmeasuring device before a pressure was reduced to 93 hPa for subsequentinjection of mercury to measure the averaged pore diameter by utilizingthe following equation.

Averaged pore diameter=2Vp/Sp,

[0103] where Vp=the pore volume (m³/g) and Sp=the specific surface area(m²/g), provided that Sp is the cumulative specific surface areaassuming that the pore is cylindrically shaped.

[0104] 2. Measurement to Re-Adsorbed Moisture Content

[0105] The lithium manganese compound oxide was dried at a temperatureof 300° C. in an air for 12 hours and then placed at a temperature of22° C. and a relative humidity of 50% for 48 hours and subsequentlyheated by a thermo-balance at a temperature rising rate of 2° C./min upto 250° C. (TGA-7) to find a reduction in weight for evaluation of there-adsorbed moisture content.

[0106] 3. Measurement to Sulfur Content

[0107] The sulfur content was measured in accordance with a regulationJIS K1467.

[0108] 4. Conditions for Charge/Discharge Tests

[0109] The prepared batteries were tested under the followingconditions.

[0110] Charge: after a constant current charge at a charge rate of 1C, aconstant voltage charge at 4.2V for 2 hours.

[0111] Discharge: a constant current discharge at a discharge rate of1C.

[0112] 500 times charge discharge cycles.

[0113] Temperature: 50° C.

[0114] Rate (%) of variation in capacity at 10th cycle form the originalcapacity.

[0115] 5. Conditions for Evaluation in Preservation Characteristics

[0116] Under the above charge/discharge test conditions, the preparedbatteries were completely charged at 4.2V and then placed at atemperature of 60° C. for 4 weeks and then cooled down to a temperatureof 25° C. for subsequent discharge to a voltage of 3.0V before thebatteries were re-charged and then re-discharged. A rate of variation indischarge capacity after the re-charge and re-discharge to before theplacement was represented by percentage.

[0117] 6. Conditions for Evaluation on Rate Characteristic

[0118] The prepared batteries were once completely charged at 4.2V andthen placed at a temperature of 25° C. for 10 days and then dischargedat discharge rates of 1C and 0.2C to measure the discharge capacity Aratio in discharge capacity of 0.2C discharge rate to 1C discharge ratewas found. TABLE 1 Averaged pore diameter (nm) cycle (%) preservation(%)  49 21 64  54 20 59  81 26 71 102 39 73 120 51 79 >200   5582 >200   48 76 >200   62 87

[0119] TABLE 2 Sulfur content (wt-%) cycle (%) preservation (%) 0.51 4976 0.44 51 79 0.43 51 79 0.41 52 79 0.36 57 80 0.32 62 85 0.21 62 870.14 63 87 0.10 65 86 0.07 66 88

[0120] TABLE 3 re-ad. moisture (wt-%) av. pore diameter (nm) cycle (%)preserve (%) 0.089  66 29 68 0.082  59 31 69 0.064  87 36 71 0.055  8944 73 0.044 105 49 76 0.037 120 51 79 0.021 160 57 80 0.013 >200   62 870.007 >200   65 86 0.004 >200   66 88

[0121] TABLE 4 sulfur moisture av. cycle preserve rate (wt-%) (wt-%) (%)(%) (%) 0.41 0.017 52 79 87.3 0.36 0.033 57 80 90.8 0.32 0.037 62 8591.9 0.21 0.021 62 87 92.0 0.14 0.010 63 87 92.2 0.10 0.013 65 86 92.20.07 0.007 66 88 92.3

[0122] Whereas modifications of the present invention will be apparentto a person having ordinary skill in the art, to which the inventionpertains, it is to be understood that embodiments as shown and describedby way of illustrations are by no means intended to be considered in alimiting sense. Accordingly, it is to be intended to cover by claims allmodifications which fall within the spirit and scope of the presentinvention.

What is claimed is:
 1. A lithium manganese oxide, wherein a content ofsulfur is not more than 0.32% by weight, and an averaged diameter ofpores is not less than 120 nanometers, and said lithium manganese oxideis represented by Li_(1+x)Mn_(2−x−y)M_(y)O₄, where “M” is at least oneof metals and 0.032≦x≦0.182; 0≦y≦0.2.
 2. The lithium manganese oxide asclaimed in claim 1, wherein said averaged diameter of pores is not lessthan 200 nanometers.
 3. The lithium manganese oxide as claimed in claim1, wherein said content of sulfur is not more than 0.10% by weight. 4.The lithium manganese oxide as claimed in claim 1, wherein if saidlithium manganese oxide is dried in at a temperature of 300° C. under anatmospheric pressure and subsequently placed a temperature in the rangeof 20-24° C. and at a relative humidity in the range of 50-60% and for48 hours, then a moisture content of said lithium manganese oxide is notmore than 0.037% by weight.
 5. A lithium manganese oxide, wherein saidlithium manganese oxide is represented by Li_(1+x)Mn_(2−x−y)M_(y)O₄,where “M” is at least one of metals and 0.032≦x≦0.182; 0≦y≦0.2, and ifsaid lithium manganese oxide is dried in at a temperature of 300° C.under an atmospheric pressure and subsequently placed a temperature inthe range of 20-24° C. and at a relative humidity in the range of 50-60%and for 48 hours, then a moisture content of said lithium manganeseoxide is not more than 0.037% by weight.
 6. The lithium manganese oxideas claimed in claim 5, wherein a content of sulfur is not more than0.32% by weight, and an averaged diameter of pores is not less than 120nanometers.
 7. The lithium manganese oxide as claimed in claim 6,wherein said averaged diameter of pores is not less than 200 nanometers.8. The lithium manganese oxide as claimed in claim 6, wherein saidcontent of sulfur is not more than 0.10% by weight.
 9. A positiveelectrode active material comprising a lithium manganese oxide, whereina content of sulfur is not more than 0.32% by weight, and an averageddiameter of pores is not less than 120 nanometers, and said lithiummanganese oxide is represented by Li_(1+x)Mn_(2−x−y)M_(y)O₄, where “M”is at least one of metals and 0.032≦x≦0.182; 0≦y≦0.2.
 10. The positiveelectrode active material as claimed in claim 9, wherein said averageddiameter of pores is not less than 200 nanometers.
 11. The positiveelectrode active material as claimed in claim 9, wherein said content ofsulfur is not more than 0.10% by weight.
 12. The positive electrodeactive material as claimed in claim 9, wherein if said lithium manganeseoxide is dried in at a temperature of 300° C. under an atmosphericpressure and subsequently placed a temperature in the range of 20-24° C.and at a relative humidity in the range of 50-60% and for 48 hours, thena moisture content of said lithium manganese oxide is not more than0.037% by weight.
 13. A positive electrode active material comprising alithium manganese oxide, wherein said lithium manganese oxide isrepresented by Li_(1+x)Mn_(2−x−y)M_(y)O₄, where “M” is at least one ofmetals and 0.032≦x≦0.182, 0≦y≦0.2, and if said lithium manganese oxideis dried in at a temperature of 300° C. under an atmospheric pressureand subsequently placed a temperature in the range of 20-24° C. and at arelative humidity in the range of 50-60% and for 48 hours, then amoisture content of said lithium manganese oxide is not more than 0.037%by weight.
 14. The positive electrode active material as claimed inclaim 13, wherein a content of sulfur is not more than 0.32% by weight,and an averaged diameter of pores is not less than 120 nanometers. 15.The positive electrode active material as claimed in claim 14, whereinsaid averaged diameter of pores is not less than 200 nanometers.
 16. Thepositive electrode active material as claimed in claim 14, wherein saidcontent of sulfur is not more than 0.10% by weight.
 17. A non-aqueouselectrolyte secondary battery having a positive electrode activematerial comprising a lithium manganese oxide, wherein a content ofsulfur is not more than 0.32% by weight, and an averaged diameter ofpores is not less than 120 nanometers, and said lithium manganese oxideis represented by Li_(1+x)Mn_(2−x−y)M_(y)O₄, where “M” is at least oneof metals and 0.032≦x≦0.182; 0≦y≦0.2.
 18. The non-aqueous electrolytesecondary battery as claimed in claim 17, wherein said averaged diameterof pores is not less than 200 nanometers.
 19. The non-aqueouselectrolyte secondary battery as claimed in claim 17, wherein saidcontent of sulfur is not more than 0.10% by weight.
 20. The non-aqueouselectrolyte secondary battery as claimed in claim 17, wherein if saidlithium manganese oxide is dried in at a temperature of 300° C. under anatmospheric pressure and subsequently placed a temperature in the rangeof 20-24° C. and at a relative humidity in the range of 50-60% and for48 hours, then a moisture content of said lithium manganese oxide is notmore than 0.037% by weight.
 21. A non-aqueous electrolyte secondarybattery, wherein a positive electrode active material comprises alithium manganese oxide represented by Li_(1+x)Mn_(2−x−y)M_(y)O₄, where“M” is at least one of metals and 0.032≦x≦0.182; 0≦y≦0.2, and if saidlithium manganese oxide is dried in at a temperature of 300° C. under anatmospheric pressure and subsequently placed a temperature in the rangeof 20-24° C. and at a relative humidity in the range of 50-60% and for48 hours, then a moisture content of said lithium manganese oxide is notmore than 0.037% by weight.
 22. The non-aqueous electrolyte secondarybattery as claimed in claim 21, wherein a content of sulfur is not morethan 0.32% by weight, and an averaged diameter of pores is not less than120 nanometers.
 23. The non-aqueous electrolyte secondary battery asclaimed in claim 22, wherein said averaged diameter of pores is not lessthan 200 nanometers.
 24. The non-aqueous electrolyte secondary batteryas claimed in claim 22, wherein said content of sulfur is not more than0.10% by weight.
 25. A method of forming a lithium manganese oxide, saidmethod comprising the steps of: mixing a manganese source and a lithiumsource to prepare a mixture; and subjecting said mixture to a baking inan oxygen-containing atmosphere.
 26. The method as claimed in claim 25,wherein said manganese source and said lithium source are mixed witheach other at a ratio of lithium to manganese in the range of 1.05 to1.30.
 27. The method as claimed in claim 26, wherein said mixture isbaked at a temperature in the range of 600-800° C. for 4-12 hours. 28.The method as claimed in claim 27, further comprising the step ofre-baking said mixture at a temperature in the range of 600-800° C. for4-24 hours.
 29. The method as claimed in claim 25, wherein saidmanganese source includes at least one selected from the groupconsisting of electrolytic manganese dioxides, chemically synthesizedmanganese dioxides, manganese oxides, and manganese salts.
 30. Themethod as claimed in claim 29, wherein said manganese source is preparedby the steps of: subjecting said electrolytic manganese dioxide, Mn₂O₃,and Mn₃O₄ to a heat treatment at a temperature in the range of 200-1000°C. in an oxygen-containing atmosphere.
 31. The method as claimed inclaim 29, wherein said manganese source is prepared by the steps of:subjecting said electrolytic manganese dioxide, Mn₂O₃, and Mn₃O₄ to acleaning with a water having a temperature in the range of 20-40° C.;and carrying out a dry process in vacuum at a temperature of 120° C. 32.The method as claimed in claim 29, wherein said manganese source isprepared by the steps of: subjecting said electrolytic manganesedioxide, Mn₂O₃, and Mn₃O₄ to a heat treatment at a temperature in therange of 200-1000° C. in an oxygen-containing atmosphere; carrying out acleaning process with a water having a temperature in the range of20-40° C.; and carrying out a dry process in vacuum.
 33. The method asclaimed in claim 29, wherein said manganese source is prepared by thesteps of: subjecting said electrolytic manganese dioxide, Mn₂O₃, andMn₃O₄ to a cleaning with a water having a temperature in the range of50-70° C.; and carrying out a dry process in vacuum at a temperature of120° C.
 34. The method as claimed in claim 29, wherein said manganesesource is prepared by the steps of: subjecting said electrolyticmanganese dioxide, Mn₂O₃, and Mn₃O₄ to a heat treatment at a temperaturein the range of 200-1000° C. boor in an oxygen-containing atmosphere;carrying out a cleaning with a water having a temperature in the rangeof 50-70° C.; and carrying out a dry process in vacuum at a temperatureof 120° C.
 35. The method as claimed in claim 29, wherein said manganesesource is prepared by the steps of subjecting said electrolyticmanganese dioxide, Mn₂O₃, and Mn₃O₄ to a cleaning with a diluted aqueousammonia; and carrying out a dry process in vacuum at a temperature of120° C.
 36. The method as claimed in claim 29, wherein said manganesesource is prepared by the steps of: subjecting said electrolyticmanganese dioxide, Mn₂O₃, and Mn₃O₄ to a heat treatment at a temperaturein the range of 200-1000° C. in an oxygen-containing atmosphere;carrying out a cleaning with a diluted aqueous ammonia; and carrying outa dry process in vacuum at a temperature of 120° C.
 37. A method offorming a lithium manganese oxide, said method comprising the steps of:subjecting an electrolytic manganese dioxide to a heat treatment at atemperature in the range of 400-900° C. in an oxygen-containingatmosphere to transfer said electrolytic manganese dioxide to amanganese oxide comprising one of β-MnO₂ and Mn₂O_(3;) subjecting saidmanganese dioxide to a water cleaning; and baking said manganese dioxidetogether with a lithium compound.
 38. The method as claimed in claim 37,wherein said manganese dioxide is baked together with said lithiumcompound at a temperature in the range of 750-900° C. in anoxygen-containing atmosphere.
 39. The method as claimed in claim 38,further comprising the step of: carrying out a re-baking process at atemperature in the range of 500-650° C. in an oxygen-containingatmosphere.